A string instrument, whether of the neck type (guitar, violin, cello, bass fiddle) or of the piano type (pianoforte, harpsichord), has a plurality of strings which are maintained taut so that when plucked, bowed, or hammered they produce a predetermined tone. These strings bear via a bridge on a resonance element, which may be the body of a guitar or a violin or the resonance board of a piano, which resonates and radiates the tone produced by the string. This bridge is normally provided adjacent the anchored end of the string, that is the fixed end of the string as contrasted to the opposite end of the string that is normally connected to a tuning pin or peg.
In order to electronically record or amplify such sounds it is best practice to provide a tone pickup directly on the instrument, rather than simply to play the instrument adjacent a microphone which would also pick up many spurious sounds. To this end it is known to mount a piezoelectric microphone directly on the sounding board of the instrument, often adjacent the bridge thereof. Such a pickup is in turn connected to the appropriate amplifying and/or recording equipment.
The difficulty with this type of system, is that the tone pickup is still relatively sensitive to external sounds, and in particular it is sensitive to acoustic feedback. This last-mentioned sensitivity is particularly prevalent when the sounds being transduced by the pickup are being amplified and played on the spot, as for instance in a concert. The amplified sounds are detected by the pickup in the manner of a positive feedback. What is more, such a pickup frequently does not produce the exact tonal quality of the instrument, yet on the other hand will amplify other sounds, such as those normally inaudible ones produced by jarring or shaking the instrument.